Endothelial cell mitogens are useful in promoting vascular tissue repair in vivo, such as blood vessel growth (angiogenesis), and vessel repair (through the replacement of damaged endothelial cells) and in stimulating endothelial cell growth on appropriate substrates for the production of blood vessels for implantation. Glioma-derived growth factor (GDGF) treatment permits the covering of synthetic polymeric vessels with non-thrombogenic vascular endothelial cells from the host animal, including man, whereby many or all of the clotting problems associated with synthetic vessel grafts are obviated. Endothelial cell stimulation with GDGF is useful for the production of vessels in vitro by growth of host vascular endothelial cells on tubular supports, for implantation back into the same host animal, including man, whereby immunological rejection of the implant will be obviated and the frequent limited supply of good vessels within the patient for transplant will be obviated. Tubular supports are coated in vitro with GDGF prior to either implantation into a host animal or coated and seeded with endothelial cells and implanted. Following implantation endothelial cells migrate into and/or grow on the artificial surface producing in vivo artificial vessels. As noted above GDGF can also be used for the stimulation or facilitation of blood vessel growth and repair in vivo, whereby the flow of blood to tissues deprived of adequate oxygen and/or other blood borne components is increased. Since GDGF can enhance vascular development and growth by the specific stimulation of vascular endothelial cells the protein can be useful in stimulating tissue repair.